In some air compressor units and other similar equipment, a hydraulic system is used to power various components of the unit. A hydraulic pump powered by an engine creates pressure and hydraulic flow and moves hydraulic fluid through the hydraulic system. Portable air compressor units are often exposed to a variety of environments, and hydraulic systems have multiple valves and circuits to control functions that allow the units to operate in extreme temperature ranges. In some prior art air compressor units, these valves are separate in the hydraulic system of the unit. Some air compressor units utilize a valve manifold that combines some of the valves, but these manifolds often require too much space, are too expensive, or do not include all of the valves in a single manifold.
Hydraulic systems for air compressor units may include heat exchangers to cool the hydraulic fluid in the hydraulic system. In some prior art air compressor units, the hydraulic system powers a fan that draws ambient air through the heat exchanger. The air passing through the heat exchanger reduces the temperature of the fluid in the heat exchanger, and the cooled fluid then returns to the hydraulic system. In some prior art air compressor units, multiple heat exchangers are used for various components of the unit. Examples of heat exchangers used in an air compressor unit include a radiator for engine coolant, fuel coolers, hydraulic oil coolers, intercoolers to cool compressed air, aftercoolers to cool discharge air, air end oil coolers, and charge-air coolers to cool turbo charged air.
A problem facing air compressor units operating in low temperatures is freezing in the heat exchangers. Like most equipment, an air compressor takes a period of time to warm-up after it is started. In cold environments, the temperature of fluid in the heat exchangers is relatively low during this initial warm-up period, and drawing cool ambient air through the heat exchanger could reduce the temperature of the fluid below its freezing point. A solution for this problem is to reduce the air drawn through the heat exchangers by blocking the air inlets or louvers. In some prior art air compressor units, the louvers are closed manually to block the air intake. Manual operation of the louvers requires a person to monitor the temperature and manually open the louvers after the temperature of the fluid in the heat exchangers increases. Closing louvers requires additional moving parts, and if the louvers are closed too long, the air compressor unit can overheat.